This invention relates to reinforced hose having a composite rubber and thermoplastic structure and to the method of making same.
It is conventional in the manufacture of higher quality hose having essentially rubber components to construct same upon either a rigid or flexible mandrel which is used not only as a support for the core, reinforcement and covering layers during application of same but also as a device for providing compressive force to the hose structure during vulcanization and for sizing the interior of the hose. Use of a rigid mandrel limits the length of a single piece of hose and the equipment which must be employed therein is complex and costly. Flexible mandrel-made hose also requires the step of removal of the mandrel from the finished product as well as the additional operations required for reuse of the mandrel materials and difficulty is encountered in retaining flexibility in the larger mandrel sizes.
Vulcanizable or thermosetting rubber hose is desirable in many instances for its favorable qualities of coupling compatibility, flexibility, kink resistance, cost of materials and the like and is superior to presently known all-plastic hoses in many of those aspects and yet still suffers a cost disadvantage due to the additional stages of manufacture, outlined previously. It is desirable to be able to combine the favorable qualities of rubber and plastic materials in a combination hose structure to utilize the advantageous properties of each material and even further advantages from the combination.
Thus, for example, in U.S. Pat. No. 3,988,189 it is described that a hybrid hose having essentially a rubber core tube may be manufactured in either a mandrel or non-mandrel process, the reinforcement and sheathing, which may be plastic, being applied after vulcanization of the core tube.
In the non-mandrel process described, it is suggested that the core tube structure may be developed with the use of a plastic liner, as of nylon or the like, over which synthetic rubber is extruded and then adhered in a subsequent vulcanization operation. The composite, cured, core tube structure may then be passed through further processes to receive bonding agents, reinforcement and sheathing materials.
While a hybrid hose structure is suggested in this reference, little attention is directed to the composite core tube structure other than to mention that adhesion between the layers can be obtained during vulcanization and that the structure is then strong enough to support further reinforcing and sheathing operations.
While it is known, for example, in U.S. Pat. No. 3,825,036 that various combinations of plastics materials may be used to form tubular structures, and that the configuration of the adjacent layers may be selected so as to achieve certain effects, i.e. appreciable bond area or an interlocking effect, or the like, apparently little attention has been directed to the development of composite core tube structures particularly suited for hoses in which reinforcement is to be utilized and in particular for hose structures which utilize a composite rubber and plastic core tube.